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The weird and wonderful flora of Madagascar

26/02/2014 11:37

Written by Daniel Austin

Madagascar and its adjacent islands harbour some 13,000 species of flowering plants of which a staggering 89% are endemic. Although some other regions of the world (such as the Tropical Andes, Indonesia and Brazil) have more plant species, they have substantially lower rates of endemism, typically below 50%. Madagascar is the world’s number one floral hotspot for an area its size, and has some unique plants to its name.

The baobab

The baobab – a freak among trees with its massively swollen trunk and sparse stubby branches – is emblematic of Madagascar. This is the motherland of baobabs. Of the nine species found worldwide, six grow exclusively in Madagascar. The others (one in Australia and two in mainland Africa) are believed to have originated from seedpods that were swept away from Malagasy shores. One of the African species can be seen in Madagascar today, for it was introduced by Arab traders as street planting in towns.

The reason for the baobab’s extraordinary girth – sometimes exceeding 30m – is that it is well adapted to inhospitably dry conditions. It is capable of taking up and storing water from sporadic downpours very efficiently, its porous wood acting like a huge sponge. No doubt inspired by the great size of some specimens, claims have been made that these giants can live for many thousands of years. It is difficult to be certain because unlike other trees baobabs do not produce growth rings, but recent radiocarbon dating suggests that the very oldest may be 900 years old, with most significantly younger.

Pachypodium

This genus contains five species from southern Africa and about 20 from Madagascar. The Malagasy pachypodiums have an unusual flower structure in that the stamens are covered by a segmented cone which must be penetrated to achieve pollination. They vary from tree-like species to caudiciforms (stem succulents) with white, red or yellow flowers. They are mostly quite spiny when young but tend to lose their spines as they mature.

The bizarrely compressed P. brevicaule, which has been likened to a sack of potatoes, has most of its large mass beneath the ground. P. lamerei – widespread in the southwest – is the most common species in cultivation. P. rutenbergianum is widely distributed from the mid-west coast to the north and is the largest species, reaching up to 15m tall with a heavily branched crown.

Carnivorous plants

There are two species of insect-eating pitcher plant (Nepenthes spp), a genus which otherwise lives only in Asia. In Madagascar’s eastern wetlands they poke out of the marsh beds like triffids planning an ambush. One of their leaves wraps upon itself to create a trumpet-shaped fly trap, which then serves up trace elements, from the flies’ remains, unobtainable from the mud below. There are also five species of sundew (Drosera spp), which possess leaves covered in sticky red tentacles that are capable of wrapping around and ensnaring any insects that become stuck to them before secreting a cocktail of enzymes to digest the prey. The semi-aquatic corkscrew plant (Genlisea margaretae) also has members of the animal kingdom on its menu. It feasts on minute microfauna caught by underground traps formed from highly modified leaves. Also present are several types of bladderwort (Utricularia spp), a group of unusual organisms that lack the distinction between root, leaf and stem organs found in most flowering plants. They are covered in vacuum-filled bladders recognised as among the most sophisticated structures in the plant kingdom. Each bladder has a small trapdoor sealed with a soft membrane that is connected to a hair trigger. When disturbed by a tiny creature, this levers open the membrane causing the partial vacuum to suck the prey inside before the door snaps shut again – all in less than a hundredth of a second. The cell then sets about extracting nutrients from its unfortunate inmate by means of digestive juices, before cleaning and repriming itself within a matter of hours.

Traveller’s palm

The traveller’s tree or traveller’s palm (Ravenala madagascariensis) is one of Madagascar’s most spectacular plants. Its elegant fronds are arranged in a dramatic vertical fan, which is decorative enough to have earned it a role as Air Madagascar’s logo. It is not a true palm but rather a member of the birdof-paradise family. It earns its common name from the relief it affords thirsty travellers: fresh water is stored in the base of its leaves and can be released with a swift blow from a machete.

Vanilla – Madagascar’s biggest export

People are often surprised to learn that vanilla ﬂavouring comes from an orchid. The Vanilla genus contains 110 species of which six are native to Madagascar, but the one grown commercially – V. planifolia – was actually introduced from Mexico.

It is an ingredient used in everything from ice cream and confectionary to cakes and Coca-Cola, as well as perfume products. But most vanilla ﬂavouring is artiﬁcial (made from wood tar or a by-product of papermaking). Synthetic vanilla is much cheaper to produce but vastly inferior; it contains only one of the aromatic components found in natural vanilla, of which at least 171 have been identiﬁed.

Real vanilla is expensive to produce because it is the most labour-intensive agricultural crop in the world. The plant grows as an evergreen vine that must be tutored along supporting trees. In its native Mexico it is pollinated by Melipona bees but in Madagascar there is no suitable insect, so in order for pods to develop every ﬂower must be pollinated by hand using a needle. Harvesting is equally labour-intensive as the pods’ development must be monitored to ensure they are picked on the right day.

They are killed by immersion in hot water for three minutes. This stops growth and initiates the enzymatic reactions responsible for the aroma. Next, these ﬂavour-developing reactions are catalysed by ‘sweating’ the pods in hot, humid conditions for at least a week. To prevent rot and to lock in the aroma, they are then dried in the sun for some weeks until they have been reduced to a ﬁfth of their original weight. The conditioning phase follows, in which the pods are stored for a few months in closed boxes while the fragrance intensiﬁes. Finally the processed pods are graded into four quality categories and bundled for export. Some growers use a pin to brand the pods with a unique series of dots to insure against theft.

Madagascar produces around 1,300 tonnes annually – more than half of the world’s supply. One hectare of vanilla yields just 60kg of ﬁnished product. Prices peaked at €400/kg in 2005 but have since crashed to less than 10% of that.